Question

Find the 69th term of the arithmetic sequence -13, -33, -53, ...​

Answer 1

-1,373

Explanation:

a69 = -13 + (69-1)(-20)

= -13+(68)(-20)

= -13 - 1,360

= -1,373

Answer 2

-1373

Explanation:

GIVEN :-

• A.P. = -13 , -33 , -53 , ...

TO FIND :-

• 69th term of A.P.

FACTS TO KNOW BEFORE SOLVING :-

Lets say there's an A.P. whose :-

• First term = a
• Common Difference = d
• Total number of terms = n
• nth term = aⁿ

Formula for finding nth term of A.P. = aⁿ = a + (n - 1)d

SOLUTION :-

According to the question ,

• First term = -13
• Common difference = -33 - (-13) = -20
• Number of terms needed to find = 69

By using the formula for finding nth term ,

69th term of A.P. = -13 + (69 - 1)×(-20) = -13 + (-1360) = -1373